An herbicide is a compound which controls or modifies plant growth, e.g., killing, retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating, and dwarfing. The term "plant" refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits. "Plant growth" includes all phases of development from seed germination to natural or induced cessation of life.
Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control can increase crop yield and reduce harvesting costs.
The most popular methods of herbicide application include: pre-plant incorporation into the soil; in-furrow application to seeds and surrounding soil; pre-emergence surface treatment of seeded soil; and post-emergence treatment of the plant and soil.
A manufacturer of an herbicide generally recommends a range of application rates and concentrations calculated to maximize weed control. The range of rates varies from approximately 0.01 to 50 pounds per acre (0.0112 to 56 kilograms per hectare (k/ha)), and is usually in the range of from 0.1 to 25 pounds per acre (0.112 to 28 k/ha). The term "herbicidally effective amount" describes an amount of an herbicide compound which controls or modifies plant growth. The actual amount used depends upon several considerations, including particular weed susceptibility and overall cost limitations.
The most important factor influencing the usefulness of a given herbicide is its selectivity towards crops. In some cases, a beneficial crop is susceptible to the effects of the herbicide. In addition, certain herbicidal compounds are phytotoxic to some weed species but not to others. To be effective, an herbicide must cause minimal damage (preferably no damage) to the beneficial crop while maximizing damage to weed species which plague that crop.
To preserve the beneficial aspects of herbicide use and to minimize crop damage, many herbicide antidotes have been prepared. These antidotes reduce or eliminate damage to the crop without substantially impairing the damaging effect of the herbicide on weed species. See U.S. Pat. Nos. 4,021,224 and 4,021,229 and Belgian Pat. No. 846,894.
The precise mechanism by which an antidote reduces herbicidal crop injury has not been established. An antidote compound may be a remedy, interferent, protectant, or antagonist. As used herein, "antidote" describes a compound which has the effect of establishing herbicide selectivity, i.e., continued herbicidal phytotoxicity to weed species and reduced or non-phytotoxicity to cultivated crop species. The term "antidotally effective amount" describes an amount of an antidote compound which counteracts a phytotoxic response of a beneficial crop to an herbicide.
Thiocarbamate and acetanilide herbicides are particularly effective in the control of grassy type weeds which interfere with the cultivation of a wide variety of crops, e.g., barley, corn, cotton lentils, peanuts, peas, potatoes, soybeans, spinach, tobacco and tomatoes. Frequently the effective use of these herbicides requires the addition of an antidote compound.